This invention relates to shirred food casings and more particularly relates to the manufacture of such food casings so that they have an improved smoother surface and so that they have less curvature along their longitudinal axes.
Shirred food casing strands have been manufactured for decades; however, the surface appearance and straightness of such strands have not always been as good as desired. Such food casing strands generally comprise tubular films which may or may not be fiber reinforced, e.g. with cellulose fibers in the form of a non-woven felt such as paper. The food casings may be manufactured of any suitable product and are most commonly manufactured from regenerated cellulose, collagen or plastic.
In using tubular food casings, a problem was almost immediately encountered during food stuffing operations where one end of the food casing was closed and food product was stuffed into the casing from the opposite open end. In particular in order to stuff more than a small portion of such a food casing, it was necessary to place an extended length of the food casing onto a stuffing horn by folding the casing in the form of pleats which are transverse to the longitudinal axis of the casing while maintaining an open bore through the folded casing to permit passage of food product from the open end. Such a folded casing was an early form of shirring.
In order to permit greater quantities of food casing to be stuffed into longer lengths of food casings, advanced shirring art was developed so that the pleated (shirred) casing could be deshirred to obtain unfolded food casing in a length of from 30 to 200 times the length of the shirred casing stick.
Numerous patents in the United States and other countries have been granted on food casing shirring technology. Examples of such patents are: U.S. Pat. Nos. 2,722,714; 2,722,215; 2,723,201; 2,983,949; 2,984,574; 3,454,983; and 3,456,286.
In all shirring operations, the exterior of the shirred strand is more or less rough due to the creases of the folds or pleats and also sometimes due to uneven folding patterns. In addition such shirred strands sometimes have a curvature due to unequal stresses on opposing sides of the casing incorporated during the shirring operation. Especially for automatic stuffing equipment and strand handling, it is desirable to have exteriors of similar strands as uniform as possible. It is further desirable to have a smooth exterior surface because of aesthetics. It is also desirable to eliminate or at least substantially reduce curvature in the strands for both automatic handling and aesthetics.